U.S. patent number 6,700,137 [Application Number 10/199,298] was granted by the patent office on 2004-03-02 for light emitting diode device.
This patent grant is currently assigned to Citizen Electronic Co., Ltd.. Invention is credited to Megumi Horiuchi, Shinobu Nakamura.
United States Patent |
6,700,137 |
Horiuchi , et al. |
March 2, 2004 |
**Please see images for:
( Certificate of Correction ) ** |
Light emitting diode device
Abstract
A light emitting diode device has a reflector member having an
approximately semispherical recess. A reflector surface is provided
on an inner surface of the recess and a light emitting diode is
provided in the recess. The light emitting diode is located at a
position so that a part of light beams emitted from the light
emitting diode recedes from an optical axis, and another part of
the light beams approaches to the optical axis.
Inventors: |
Horiuchi; Megumi
(Yamanashi-ken, JP), Nakamura; Shinobu
(Yamanashi-ken, JP) |
Assignee: |
Citizen Electronic Co., Ltd.
(Yamanashi-ken, JP)
|
Family
ID: |
19058239 |
Appl.
No.: |
10/199,298 |
Filed: |
July 22, 2002 |
Foreign Application Priority Data
|
|
|
|
|
Jul 25, 2001 [JP] |
|
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2001-225211 |
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Current U.S.
Class: |
257/81; 257/432;
257/E33.072 |
Current CPC
Class: |
H01L
33/60 (20130101); H01L 33/483 (20130101); H01L
2224/48091 (20130101); H01L 2224/48091 (20130101); H01L
2924/00014 (20130101) |
Current International
Class: |
H01L
33/00 (20060101); H01L 027/15 (); H01L
031/023 () |
Field of
Search: |
;257/81,80,82,88,91,99,100,432 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Fahmy; Wael
Assistant Examiner: Trinh; Hoa B.
Attorney, Agent or Firm: Dennison, Schultz, Dougherty &
MacDonald
Claims
What is claimed is:
1. A light emitting diode device comprising: a reflector member
having a recess with an opening which comprises a first part
extending in an X-axis direction, and a second part extending in a
Y-axis direction, the first part having greater length than the
second part; a reflector surface provided on an inner surface of
the recess; the reflector surface comprising a first reflector
surface about the X-axis and a second reflector surface about the
Y-axis; the first reflector surface having a first parabola having
a first focus, and the second reflector surface having a second
parabola having a second focus; a light emitting diode provided in
the recess; and the light emitting diode being located at a
position with respect to the first and second foci so that light
reflected by the first reflector surface recedes from an optical
axis, and light reflected by the second reflector surface
approaches to the optical axis.
2. The device according to claim 1 further comprising a substrate,
and the reflector member being mounted on the substrate.
3. The device according to claim 1 wherein the light emitting diode
is located at a position between the first focus of the first
parabola and the second focus of the second parabola.
4. The device according to claim 3 wherein a focal distance of the
parabola about the X-axis is longer than a focal distance of the
parabola about the Y-axis.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a light emitting diode device
having a light emitting diode and provided for an electronic
equipment, and more particularly to a light emitting diode device
having a reflector.
FIG. 26 is a perspective view showing a conventional light emitting
diode device, and FIG. 27 is a sectional view of the light emitting
diode device.
The light emitting diode device comprises a substrate 101 made of
an epoxy resin, a cathode electrode pattern 102 and an anode
electrode pattern 103 formed on the upper surface of the substrate
101. These patterns 102 and 103 are connected to underside patterns
102a and 103a through leads 104 provided in through-holes.
A light emitting diode 105 is securely mounted on the cathode
electrode pattern 102. The light emitting diode 105 is connected to
the anode electrode pattern 103 by a bonding wire 109. A
cylindrical reflector 106 is mounted on the substrate 101
surrounding the light emitting diode 105. An inner reflecting wall
107 has an inverted truncated cone shape, so that the light 108
emitted from the light emitting diode 105 in horizontal directions
is reflected in vertical directions.
The light emitting diode (LED) 105, reflector 106, and bonding wire
109 are sealed by a sealing member 110 made of a transmissive
resin.
The sealing member 110 has a semispherical lens 110b. The
semispherical lens 110b is provided for condensing the light 108
into light 108b.
FIG. 28 is a perspective view showing another reflector, and FIG.
29 is a sectional view of the reflector.
The reflector 116 has a semispherical reflecting wall 117 so as to
parallely reflect the light emitted from the LED 105 in vertical
direction.
Although the light emitting diode device illuminates a small area,
the device can not light a large area. Therefore, the device can
not be used as an edge light for irradiating a panel.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a light emitting
diode device which may irradiate a wide area.
According to the present invention, there is provided a light
emitting diode device comprising a reflector member having an
approximately semispherical recess, a reflector surface provided on
an inner surface of the recess, a light emitting diode provided in
the recess, and the light emitting diode being located at a
position so that a part of light beams emitted from the light
emitting diode recedes from an optical axis, and another part of
the light beams approaches to the optical axis.
In an aspect of the present invention, the device comprises a
substrate, and the reflector member being mounted on the
substrate.
The reflector surface includes a first reflector surface about an
X-axis and a second reflector surface about a Y-axis.
In another aspect, the first reflector surface and the second
reflector surface are different in curvature.
The first and second reflector surfaces comprise same parabolas,
both parabolas are disposed so as to be different in position of
focus.
The reflector surface has a rectangular shape in plan view, and the
reflector member comprises four reflector surfaces divided by a
pair of diagonal lines.
These and other objects and features of the present invention will
become more apparent from the following detailed description with
reference to the accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a graph showing a parabola in an XZ-plane of an XYZ
orthogonal coordinate system;
FIG. 2 is a graph showing a parabola in a YZ-plane of the
orthogonal coordinate system;
FIG. 3 is a plan view of a light emitting diode device according to
a first embodiment of the present invention as viewed from a Z
direction;
FIG. 4 is a sectional view of the device taken along an X-line;
FIG. 5 is a sectional view taken along a Y-line;
FIG. 6 is a sectional view of a bundle of rays;
FIG. 7 shows an XYZ orthogonal coordinate system;
FIGS. 8 and 9 are graphs showing the positions of the focus P;
FIG. 10 is a plan view showing a reflector member in the second
embodiment of the present invention;
FIG. 11 is a perspective view of the reflector member;
FIG. 12 is a sectional view taken along the X-line of a light
emitting diode device based on the reflector member of FIG. 10;
FIG. 13 is a sectional view of the device taken along the
Y-line;
FIG. 14 is a graph showing a principle of the third embodiment of
the present invention;
FIGS. 15 and 16 are sectional views of a light emitting diode
device of the third embodiment;
FIG. 17 is a plan view of the fourth embodiment;
FIG. 18 is a sectional view taken along the X-line;
FIG. 19 is a sectional view taken along the Y-line;
FIG. 20 is a plan view of the fifth embodiment;
FIG. 21 is a sectional view taken along the X-line;
FIG. 22 is a sectional view taken along a ridge line r;
FIG. 23 is a sectional view taken along the Y-line;
FIG. 24 is a sectional view of a bundle of rays;
FIG. 25 is a sectional view of a light emitting diode device of the
sixth embodiment of the present invention;
FIG. 26 is a perspective view showing a conventional light emitting
diode device;
FIG. 27 is a sectional view of the light emitting diode device;
FIG. 28 is a perspective view showing another reflector; and
FIG. 29 is a sectional view of the reflector.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The principle of the present invention will be described
hereinafter.
FIG. 1 is a graph showing a parabola in an XZ-plane of an XYZ
orthogonal coordinate system, and FIG. 2 is a graph showing a
parabola in a YZ-plane of the orthogonal coordinate system.
Referring to FIG. 1, the parabola S1 is expressed by the following
equation of parabola
where p1 is the focal distance from the origin PO to the focus
P1.
Here, if the parabola S1 is a parabolic mirror, light beams emitted
from a light source located at the focus P1 are changed by the
parabolic mirror to light beams parallel with the Z-axis (optical
axis) as shown by solid lines. However, if the light source is
located at a point Pm deflected from the focus P1 to the origin PO,
the light beams from the light source are changed to light beams
receding from the Z-axis as shown by dotted lines, thereby
expanding the bundle of rays in the XZ-plane.
Referring to FIG. 2, the parabola S2 is expressed by the following
equation of parabola,
where p2 is the focal distance from the origin PO to the focus
P2.
In the parabola Y.sup.2, the focal distance p2 is smaller than the
focal distance p1 (p2<p1). Therefore, the curvature of the
reflector (inverse number of radius of curvature) of the parabola
S2 is larger than that of the parabola S1.
When the light beams emitted from the focus P2 strike the parabola
S2, the light beams are changed to light beams parallel with the
Z-axis as shown by solid lines. However, if the light source is
located at a point Pm distant from the origin PO, the light beams
from the light source are changed to light beams approaching the
Z-axis as shown by dotted lines, thereby reducing the bundle of
rays in the YZ-plane.
Consequently, if a reflector having the parabola S1 in the XZ-plane
and the parabola S2 in the YZ-plane is prepared, and a light source
is located at the point Pm between the focus P1 of the parabola S1
and the focus P2 of the parabola S2, the bundle of rays reflected
from the reflector is wide in the XZ-plane and narrow in the
YZ-plane.
The present invention is based on the above described
principle.
FIG. 3 is a plan view of a light emitting diode device according to
a first embodiment of the present invention as viewed from the Z
direction, FIG. 4 is a sectional view of the device taken along the
X-line, FIG. 5 is a sectional view taken along the Y-line.
The light emitting diode device 10 comprises a substrate 2 made of
an epoxy resin, a cathode electrode pattern 3 and an anode
electrode pattern 4 formed on the upper surface of the substrate 2.
These patterns 3 and 4 are connected to underside patterns through
leads provided on side walls of the substrate 2.
A light emitting diode 1 is securely mounted on the substrate 2. A
reflector member 5 made of resin has an approximately semispherical
recess and is mounted on the substrate 2 surrounding the light
emitting diode 1. The reflector member 5 has a reflector surface 5a
formed on the inner surface of the semispherical recess. The
reflecting surface 5a comprises a parabola S1 having a focus at a
point P1, and a parabola S2 having a focus at a point P2. The light
emitting diode 1 is located at a point between the points P1 and
P2. The parabolas S1 and S2 are cut at the upper surface of the
substrate 2 to form an opening 5c as shown in FIG. 5.
The reflector surface 5a is coated with a shine Ag plating. A
cathode lead pattern 6 and an anode lead pattern 7 are formed on
outside walls and underside of the reflector member 5. The cathode
and anode of the light emitting diode 1 are connected to a terminal
6b of the cathode lead pattern 6 and to a terminal 7b of the anode
lead pattern 7 by bonding wires 8. The cathode lead pattern 6 and
anode lead pattern 7 are connected to the cathode and anode
electrode patterns 3, 4 at the undersides thereof.
The bonding wires 8 and the light emitting diode 1 are sealed by a
sealing member 9 made of a transmissive resin charged in the recess
of the reflector member 5.
When an electric current is applied to the light emitting diode 1
through electrode patterns 3, 4, lead patterns 6, 7 and bonding
wires 8, the light emitting diode 1 emits light. Light beams
reflected by the reflector surface 5a having the parabola S1 are
expanded as shown in FIG. 4, and light beams reflected by the
reflector surface 5a having the parabola S2 are reduced as shown in
FIG. 5. Thus, as shown in FIG. 6, the section 12 of the bundle of
rays has an elongated ellipse.
Referring to FIG. 7, a line a is a cutting line for cutting the
reflector member 5. The cutting line a is rotated 180 degrees about
the Z-axis in FIG. 3 in order to obtain a parabola in each
section.
FIG. 8 is a graph showing the positions of the focus P. The line A
shows the change of the focus. For example, when
.theta.=45.degree., the focus P is at an intermediate position
between the focus P1 and P2.
FIG. 10 is a plan view showing a reflector member in the second
embodiment of the present invention, and FIG. 11 is a perspective
view of the reflector member.
The reflector member 15 comprises a first parabola area 15a1 having
the parabola S1 and a second parabola area 15a2 having the parabola
S2. In particular, the whole area of the first parabola area 15a1
is formed by the parabola S1, and the whole area of the second
parabola area 15a2 is formed by the parabola S2.
The first parabola area 15a1 is disposed about the X-axis and the
second parabola area 15a2 is disposed about the Y-axis.
The second parabola area 15a2 is located at a position near the
Z-axis. Therefore, there is formed steps 16 between both areas.
FIG. 12 is a sectional view taken along the X-line of a light
emitting diode device based on the reflector member of FIG. 10,
FIG. 13 is a sectional view of the device taken along the Y-line.
The same parts as the device of FIGS. 4 and 5 are identified by the
same reference numerals as FIGS. 4 and 5.
Positions of focuses P1 and P2 do not change as shown by a line B
of FIG. 8.
FIG. 14 is a graph showing a principle of the third embodiment of
the present invention. FIGS. 15 and 16 are sectional views of a
light emitting diode device of the third embodiment.
The light emitting diode device 30 has two parabolas S11 and S12
each of which has the same focal distance p1 as shown in FIG. 14.
However, the parabola S12 is shifted from the X-axis distance d
which is longer than the focal distance p1. The parabola S11 is
provided on the X-axis and parabola S12 is disposed on the Y-axis.
The light emitting diode 1 is located between the focus P1 of the
parabola S11 and the origin P0 of the parabola S11. Therefore,
light beams discharge in the same directions as previous
embodiments as shown in FIGS. 15, 16.
FIG. 17 is a plan view of the fourth embodiment, FIG. 18 is a
sectional view taken along the X-line, and FIG. 19 is a sectional
view taken along the Y-line.
In a light emitting diode device 40, there is not provided the
substrate 2 in FIG. 4 of the first embodiment. A reflector member
35 is downwardly extended and a reflector surface 35a has a flat
bottom 35c. The light emitting diode is mounted on the bottom 35c.
Other parts are the same as the first embodiment.
FIG. 20 is a plan view of the fifth embodiment. FIG. 21 is a
sectional view taken along the X-line, FIG. 22 is a sectional view
taken along a ridge line r, and FIG. 23 is a sectional view taken
along the Y-line.
A light emitting diode device 50 has a reflector member 45 having a
construction similar to the reflector member 35 of the fourth
embodiment. The reflector member 45 has a rectangular shape
elongated in the X-axis in plan view, and comprises four reflector
surfaces 45a, 45b, 45c and 45d. The reflector surfaces 45a and 45c
are formed by the parabola S1, and reflector surfaces 45b and 45d
are formed by the parabola S2. Between adjacent reflector surfaces
the ridge line r is forms. Opposite ridge lines r formed a parabola
s3.
FIG. 9 shows the position of the focuses P of the parabolas S1, S2
and S3. When the angle .theta. of the line a (FIG. 7) is zero
(.theta.=0.degree.), the focus position is P1 at a position C1 on a
line C. As the angle .theta. increases, the position P becomes
high. At a position C3 (.theta.=about 30.degree.), the position P
is a maximum P3 of the parabola S3. The parabola S3 is gentle
compared with the slope of the parabola S1 as shown in FIG. 22.
When the angle .theta. further increases, the position P becomes
low. At a point C2, the position P becomes lowermost of the
parabola S2 at focus P2.
In the present embodiment, there is provided a region Ch (FIG. 9)
where the focal distance p becomes larger (P3) than the focal
distance p1. Therefore, light beams are further expanded from the
Z-axis as shown in FIG. 22. Thus, the sectional shape of the bundle
of rays expands to a rectangular shape elongated in the X-line as
shown in FIG. 24. Consequently, a large rectangular area is
uniformly illuminated.
FIG. 25 is a sectional view of a light emitting diode device of the
sixth embodiment of the present invention.
In the light emitting diode device 60, the bonding wire 8 for the
cathode and the cathode leading pattern 6 in the first embodiment
are omitted. The cathode of the light emitting diode 1 is directly
connected to the cathode electrode pattern 3 by die bonding. Other
construction is the same as the first embodiment.
While the invention has been described in conjunction with
preferred specific embodiment thereof, it will be understood that
this description is intended to illustrate and not limit the scope
of the invention, which is defined by the following claims.
* * * * *